Acceleration of vulcanization of rubber



Patented Mar. 8, 1938 UNITED STATES ACCELERATION OF VULCANIZATION OF RUBBER Ludwig Orthner, Leverkusen-on-the-Rhine, and

Ewald Zaucker,

Cologne-Mulheim-on-the- Rhine, Germany, assignors to I. G. Farbenindustrie Aktiengesellschaft, Frankfort-on-the- Main, Germany No Drawing. Original application June 1931, Serial No. 546,417.

23, Divided and this application July 1, 1932, Serial No. 620,527. In Germany June 28, 1930 1 Claim.

The present invention relates to a process of vulcanizing rubber and to the vulcanizates obtainable by said process.

Mercapto arylene thiazoles have already been suggested for accelerating vulcanization. This class of substances, however, possesses the disadvantage of an unfavorable critical temperature, that is to say, the use; thereof involves the danger of a premature commencement of the vulcanization.

In accordance withthe present invention natural rubber or artificial rubber-like masses obtainable, for example, by polymerizing butadiene or another homologue or an analogue of butadiene, are vulcanized with the addition of vulcanization accelerators possessing considerably more favorable critical temperatures, said new vulcanization accelerators having the probable general formu1a:-

of the probable general formula:-

Eel-O y wherein Hal stands for a halogen atom, :1: stands for an oxygen or sulfur atom, and 1 stands for a halogen atom, aryl or alkoxy to react with at least an about molecular quantity of a -mercapto arylenethiazole, as is more fully described in the annexed examples.

As suitable compounds of the general formula Z Hal-O y coming into consideration for the purpose of the invention, there may be mentioned by way of example:- phosgene, chloroformic acid methylester: C1-COOCI-I3; chloroformic acid ethylester:

C1.CO.OC2H5 chloroformic acid propylester:

chloroformic acid isopropylester:

Cl.CO.OCI-I(CH3) z;

chloroformic acid butylester:

C1.C'O.OC4H9 chloroformic acid amylester:

C1.C0.0C5H11;

chloroformic acid benzylester:

C1.C0.0CH2.C6H5

chloroformic acid betachloroethylester:

C1.C().OCH2.C'H2C1;

chloroiormic acid cyclohexylester:

Cl.CO.CeH11;

benzoylchloride:

C1-CO.CsI-I5;

para-nitrobenzoylchloride:

C1.CO.C6H4NO2;

para-chlorobenzoylch1oride Cl-CO.CsI-I4Cl;

2.4-dichlorobenzoylchloride Cl.CO.CeI-I3Cl2;

para-methoxybenzoylchloride C1.CO.C6H4(OCH3) 2-chloro-5-nitrobenzoylchloride:

nitro-para-toluylic acid chloride:

paratolyl-2-benzoylchloride:

C1.CO.C6H4.C6H4.CH3

chlorobenzoyl-2-benzoylchloride:

Cl.CO.CsH4.CO.CsI-I4.Cl;

The new accelerators are generally colorless to yellowish crystalline substances, insoluble in water, soluble in the usual organic solvents, and are particularly valuable in view of their favorable critical temperatures.

For vulcanization purposes the new vulcanization accelerators are incorporated within the rubber (which term is intended to include natural rubber as well as artificial rubber-like masses, derived, for example, from, butadiene, isoprene, dimethylbutadiene or another homologue or analogue of butadiene) in any desired manner, for example, by rolling or kneading. Obviously, a vulcanizing agent, such as sulfur, agents being able to split off sulfur, selenium etc. is likewise added, and if desired, other ingredients known to favorable influence rubber-vulcanization processes or the properties of the vulcanizates obtainable may be admixed to the vulcanization mixture. The latter is then vulcanized in the usual manner by heating it to a temperature sufficient to perform vulcanization, for example, to a temperature between about -170 C.

Representatives of this new class of accelerators, which possess too low a velocity on hot vulcanization, can be adjusted to give more favorable times of heating by combination with stearic acid and/or with appropriate accelerators of separates directly in the reaction; after washing with water it shows the melting point of 276 C.

Example 3 The condensation product from ,u-mercapto benzothiazole (sodium salt) and chloroformic acid methylester (I in the table) was tested as accelerator in the following mixture:--

Parts by weight classes other than that of the present invention Crepe 100 especially basic accelerators while preserving a Zinc oxide 5 satisfactory critical temperature. sulfur 3 The following examples will illustrate the instearic acid 1 5 vention without, however, restricting it thereto Accelerator L03 Example 1 To a solution of 100 grams of wmercapto benzothiazole and 24 grams of sodium hydroxide in 200 cos. of methyl alcohol, 65 grams of chloroformic acid ethylester (I) or 56,5 grams of the condensation product from ,u-mercapto benzothiazole (sodium salt) and chloroformic acid ethylester (II in the table) was tested in the following mixture:-

chloroformic acid methylester (II) are dropped, Parts by wei the reaction mixture is boiled for 5 minutes and C' p 100 poured on to ice. After recrystallization from Zinc ox de 5 petrolether the condensation product obtained Sulfur 3 with the ethylester (I) has the melting point of Stearic acid 1.8 66 0., the condensation product obtained with Accelerator 1.15

the methylester (II) has the melting point of 56 C. The reaction proceeds according to the following equation:

Example 2 Into a solution of 100 grams of -mercapto the condensation product from -mercapto benzothiazole (sodium salt) andphosgene (III in the table) was tested in the following mixture:-

benzothiazole and 24 grams of sodium hydroxide Crepe Parts by a s in 200 cos. of acetone, 84 grams of benzoylchloride Zinc g g; 5 are dropped in slowly. On diluting the reaction sulfur 3 mixture with water the reaction product of the g' ai: 1.5 f u Accelerator and having a melting point of 130 C. is precipitated Parts by weight I When substituting the 8 1 grams of benzoyl- 100 chloride by 111 grams of para-nitrobenzoyl- Zmc oxldea n 5 chloride, the compound of the formula --"f 3 Steanc acid 1.5 N Accelerator 1.0

C 8 CO The following values were obtained A=tensile strength in kg. per sq. cm. B=stretch in percent.

Heating I II III IV V Press. Minutes ab. A B A B A B A B A B 7 atm 30 0.5 43s 5n 20 2.0 1015 0a 1000 Not tested 00 2.0 150 933 100 91s Nottestad 1 3. 0 102 887 115 004 1118 35 3. 0 133 852 139 868 With the mixture:-

Parts by weight Crepe 100 Zinc oxide -5 Sulfur 3 Stearic acid 1 Diphenylguanidine 0.2 Accelerator 0.8

the following values were obtained:-

Heating II IV Minutes Press- A B A B ahatm.

This is a division of our co-pending application Serial No. 546,417, filed June 23, 1931.

We claim:-

The process of treating rubber which comprises vulcanizing a rubber mix to which has been added diphenylguanidine and a product obtainable by reacting a Z-mercaptobenzothiazole with ethyl chloroformate.

LU'DWIG ORTHNER. EWALD ZAUCKER. 

